First you need to download the boards information for the Arduino IDE. This file will need to be downloaded in order to program a ATtiny2313. http://www.mediafire.com/download/ju012s124w4gbl2/tiny.zip
Once you have downloaded that you will need to extract the 'tiny' folder to your Arduino hardware folder. Now if you don't know where that is or if you don't have it here are the steps.
Go to your Arduino documents. This is where all the sketches are saved (by default).
For mac users it's Macintosh HD>Users>username>documents>Arduino.
Create a new folder and name it "hardware", just like that. Into this folder you will put the 'tiny' folder that you downloaded.
For PC usersProgram Files(x86)=>Arduino=>hardware. Copy the 'tiny' folder into it and restart the Arduino IDE.Delete the extra mac content.
First make sure that you have already uploaded the ArduinoISP to the Arduino.
Select the (ATtiny2313@1MHz) board. When you go to boards you will notice that you will have a lot more options to use. This is because that 'tiny' folder that we put in the 'hardware' folder gave the Arduino program more board options.
Under 'programmer' select 'Arduino as ISP'.
Open the blink sketch and change the led pin 13 to pin 7.
Click the upload button and pray!
Once you upload it you should have no errors. If you connected the Attiny to the Arduino incorrectly, it'll bring up the an error and it will say 'double check connections'.
After upload your LED should start blinking! Congrats! You now know how to program your ATtiny2313.